A thin convex lens L is positioned midway between two diaphragms: D₁, 4.0 cm to its left, and D₂, 4.0 cm to its right. The lens has a diameter of 12 cm and a focal length of 12 cm. The holes in D₁ and D₂ have diameters of 12 cm and 8.0 cm, respectively. An axial object point is 20 cm to the left of D₁. 

(a) What is the image of D₁ in the object space (i.e., as imaged by any lens to its left with light traveling left)?

(b) What is the image of L in the object space?

(c) What is the image of D₂ in the object space? Give the size and location of that aperture’s image.

(d) Locate the entrance pupil and the aperture stop.